When it comes to charismatic megafauna, polar bears are right up there in terms of cute stuff people like to like. Lately they have also been the poster-bear against climate change. That makes sense, considering that polar bears (Ursus maritimus) occur only in the Northern Hemisphere and are dependent on sea ice for access to their marine mammal prey, mainly seals. Declines in summer sea ice have been associated with declining physical stature, declining physical condition, poorer survival rates, and declining population sizes for these bears. This sea ice decline has been linked to these declines.

A new paper this week in Nature uses projections of twenty-first century global mean surface air temperature (GMAT) and data from the Community Climate System Model (CCSM3) to test the hypothesis that a tipping point will lead to irreversible loss of seasonal ice habitat as GMAT increases. Basically, that there are some elements/variables within a system that, when changed enough, cause habitats that support cold-dependent species to disappear abruptly and irreversibly. Namely when a particular GMAT is exceeded.

In a nutshell, they tested whether mitigating the rise in greenhouse gases could improve the outlook for polar bears.

Now, a USGS study in 2007 concluded that two-thirds of the world's polar bears could disappear by 2050 if atmospheric temperatures continue to increase due to greenhouse gases. Their model was a general circulation model (GCM) that projected losses of Arctic sea ice based on the Special Report on Emissions Scenarios (SRES) and a "business as usual" greenhouse gas emissions scenario, where emissions continue to increase and the carbon dioxide concentration reaches 689 parts per million (ppm) by the end of the century. However, they did not consider the possible benefits of greenhouse gas mitigation. Think about that in terms of tipping points. If you mitigate too little and/or too late then you get no conservation benefits for polar bears as their ice would already be gone. If you mitigate more and/or soon enough then you save the ice and the bears. That's the thought anyway. So the researchers modeled 5 different scenarios that ranged from "business as usual" all the way to aggressive cuts that reduce carbon dioxide concentrations to 368 ppm, those seen in the year 2000.

The study concludes that mitigating the rise in greenhouse gases will result in substantially more sea ice habitat being retained. The business-as-usual-model shows a 50% loss of sea ice by 2050 whereas the aggressive-mitigation-model shows only a 20% loss. They also show that this habitat retention, in turn, will allow polar bears to persist throughout the century in greater numbers and in more areas. The business-as-usual-model shows a 50-80% chance of polar bears disappearing from these habitats whereas the aggressive-mitigation-model shows only a 25-50% chance. However, the models did not give the thresholds or tipping point values that will lead to irreversible ice loss. They found that sea ice will decline at a steady rate as global mean annual temperature rises.

The paper also addresses positive feedback in this system. Its all about albedo, or how strongly a surface reflects light. Its really a quite logical scenario. Ice reflects light very well, warmer temperatures cause ice to melt, retreating ice means less reflective surface, retreating ice also means more exposed water, the darker water absorbs more sunlight, more absorbed light increases temperatures, increased temperatures melt more ice. And so on and so on. In this paper they test models that might counter this feedback mechanism. They specifically refer to rapid ice-loss events (RILEs). These rapid freezes result from going from open water to cold conditions reappearing in the Fall, and these compensate for the effects that are working to provide the potential tipping points.

Polar bears are not out of the woods yet. After all, we are still running the business-as-usual-model. And, in the past, models predicting sea ice loss have fallen short. But this paper shows us some good news, that with proper mitigation we can potentially slow down the decline.

Monday, December 20, 2010

This story is about tracks, specifically dinosaur tracks. Footprints can be very informative, giving so much more information than just the shape of the foot. They provide information on species, body posture, locomotor ability, sociality, preferential environments, and stratigraphic and geographic faunal diversity.

As you might guess, it isn't always easy to identify fossilized dinosaur tracks. Sure, some species are easier than others like sauropods, stegosaurs, and ceratopsians. The difficulty arises in distinguishing bipedal theropods (carnivores walking on two legs) and ornithopod dinosaurs ("bird-hipped" dinos, grazers walking/running on two legs). You can see how they might look pretty similar.

A new, in press, paper in Cretaceous Research takes a look at the Dinosaur Stampede National Monument at Lake Quarry Conservation Park in central-western Queensland, Australia. This monument contains thousands of fossilized footprints of dozens of dinosaurs from the mid-Cretaceous. Since the 1970's, the popular hypothesis regarding this area is that an Allosaurus-sized dinosaur chased a mixed herd of small-bodied dinosaurs, causing a stampede. Previous studies have identified this "predatory protagonist" as a large tridactyl (three-toed) dinosaur, a theropod (likely a Tyrannosauropus). This particular taxon has a bit of a checkered history, scientists have argued about it since the early 1920's. It has also been proposed that the tracks on the monument are attributable to a hadrosaurid ornithopod (a duck-billed dinosaur that walked on two legs).

Figure 1. The Winton Formation at Lark Quarry.

These authors applied a multivariate analysis to discriminate between theropod and ornithopod tracks in order to identify the track maker. Multivariate analysis allows you to analyze more than one statistical variable at a time and therefore you are able to test multiple dimensions while taking into account several variables. Why mention the statistical test used? Some people like statistics. No really, I mentioned it because this is the first time that multivariate analysis has been used to identify tracks on this valuable piece of biological history. To perform this analysis the researchers measured all of the tracks using published line drawings, catalogued photographs, latex peels, museum casts, and actually measured the real ones themselves. The variables for the analysis included track length and width, total digit lengths, basal digit length and width, middle digit widths, and the distance from heal to the interdigital (hypex) point.

The results showed that a majority of these measurements fell within the threshold expected for ornithopod dinosaurs. In fact, the authors conclude that of the known types of theropods from this region, none of the body fossils adequately match the measurements and analyses that they did.

So what type of ornithopod was the track maker? Well, the footprints are slightly longer than they are wide, they have symmetrical toes, have claws, and have a V-shaped central digit. Of the known large Cretaceous ornithopods, previous studies have concluded that it could be either Ambyldactylus, Caririchnium or Iguanodonipus. Of these, only the iguanodontian dinosaur, Amblydactylus, shares the distinctive features exhibited in the Lark Quarry tracks. The tracks are remarkably similar to ornithopod tracks from Canada named Amblydactylus gethingi and so the authors suggest re-naming the Lark Quarry tracks Amblydactlyus cf. A. gethingi. In all likelihood, the footprints were made by a large ornithopod standing approximately 2.5 meters tall at the hips, likely a more primitive member of the group, probably similar to Muttaburrasaurus langdoni. This species specifically because it has been found in similarly aged rocks only a few hundred kilometers from Lark Quarry. The stampede of the smaller dinosaurs also represented in these rocks was probably due to the approach of this larger dinosaur. A large herbivore spooking a group of smaller dinosaurs is not exactly as exciting as a predator chasing them down but, in this case, is more accurate.

The authors state that if this identification is correct then it removes any published evidence that a large theropod dinosaur existed in the Australian Cretaceous. However, I do recall posting an article about a new theropod discovered in Australia from 110 million years ago - which I'm pretty sure is the Cretaceous period (144 to 65 million years ago?) - so I'm not sure about this wiping out all evidence thing. Just sayin'.

This is the paper:
Romilio, Anthony and Steven W. Salisbury (2010). A reassessment of large theropod dinosaur tracks from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia: A case for mistaken identity. Cretaceous Research: in press. (DOI: 10.1016/j.cretres.2010.11.003)

Google. Love Google. It does so much, including powering this blog. They are known for their great mapping technologies such as Google Earth. Now they tackle a new mapping challenge: The human body. Last Thursday marked the release of Body Browser.

Body Browser uses 3D graphics application programming interface WebGL running within a browser to create a three-dimensional model that allows users to zoom in and out of the human body, remove layers, and generally explore. It is searchable and clickable, giving all sorts of info on how the body is put together.

Body Browser doesn't require Java or Flash, but you will need a browser that supports WebGL. Google recommends using the most recent version of Chrome, but Safari and Firefox/4.0b1 work as well. Body Browser is still in beta and has not been officially released, but users are able to try it out and report problems and bugs. So keep an eye out for this program to become fully operational.

Having so thoroughly enjoyed this list I looked to see if there were any more. As it turns out the same journal publishes this type of list annually. I freely admit that I like the negative reviews best, you gotta admit they are the funniest. Here are a few of my favorites from years past, and at the end is the references/links so you can read the complete lists.

From 2009:

Some self citations may be easily taken out without harming the paper.

The peaceful atmosphere between Christmas and New Year was transiently disrupted by reading this manuscript.

Ribosomes do not contain DNA.

Page 3, line 28 –‘arqueobacteria’?

I am afraid this current version looks too much like another manuscript saying ‘gee whiz we looked in a strange place and found some new microbes’.

The writing style is flowery and has an air of Oscar Wilde about it.

The trees are crap but, besides this, excellent work.

From 2008:

Mouldy bread. Unfortunately there are too many technical flaws in this one. Too bad because the potential was high.

Great organism. Great scientists. Terrible manuscript.

I am fed up with people ignoring totally the instructions for authors.

The Abstract describes results that I could not find in the Results section.

I wonder if you and I do not have better things to do than help people who can't help themselves.

They were not the first to have done this, but they don't seem to know that.

I have found this ms. boring to death.

‘Hijacked’ is a very dramatic word; maybe the bacteria are more polite with their biosynthesis.

Page X, line Y claims both ‘rare’ and ‘unusual.’ Madonna and Tony Blair might use both in the same sentence.

From 2007:

I felt like I was teaching my grandmother to suck eggs. Accept with minor revision.

The paper is full of wild speculation linked by a few random experiments.

A bad paper containing a good idea.

Hundreds of commas are missing!

A highly relevant, beautifully and concisely written cross-disciplinary report that unfortunately comes with a dull abstract.

Use of the term remarkably borders on dramatization.

For this crucial initial step, authors behaved like a cook who is in charge of preparing an ‘haute cuisine’ meal for the 40th wedding anniversary for 100 guests and consults the first cookbook for kiddies to get some idea.

I nearly said reject. But then I recalled that I have a hangover and I am feeling grumpy.

From 2006:

I have taken out my earlier comment that the authors retake Chemistry 101, that is probably not allowable.

The authors assume. . . . All assumptions are wrong.

The authors need to remember that adverbs in English tend to end in -ly.

The work is basically sound but unfortunately the presentation is a bit of a dog's breakfast.

This is an essentially unreadable paper sent to the wrong journal.

Fig. 1a looks a bit hand-drawn, 1b has more axes than display area.

There is no apparent study concept other than ‘we went out to the campus pond one day and took 2 samples for sequencing’.

From 2005:

This is depressing! So much work with so little science.

They have no clue what they write about.

The authors are quite creative in using different statistical approaches.

This paper is the very expression of what happens when one tries to chop up one piece of work into as many publications as possible.

Why don’t the percentages . . . add up to 100%?

Almost all references used by the authors are from the last century.

Since I'm only posting a subset of each list I went ahead and looked at 5 years. There are more, and they get addictive once you start reading. So if you like them then look up some more, they are always published in the last issue of December. Have fun!

Monday, December 13, 2010

This video is really long, but at the same time really interesting. It is a narrated video from NASA showing the best of the ground-based Space Shuttle motion imagery from STS-114, STS-117, and STS-124 missions. Such imagery is taken during each mission in order to visually identify off-nominal events and conditions requiring corrective action to ensure mission safety and success. So celebrate 30 years of the Space Shuttle Program by learning a little more about the Space Shuttle Program.

Saturday, December 11, 2010

Once again, I'm going to ask you to close your eyes and picture this: your perfect mate. If you were to describe him/her to me how would you do so? Hair, eyes, and skin color? Height and build? Think about it while we go through a short sexual selection primer.

Natural selection produces changes in the genetic composition of a population from one generation to the next. These changes occur as traits become more or less common in a population due to effects on the survival and reproduction of the individuals within that population/species. There's all kinds of mechanisms and processes involved in natural selection, but we are going to focus on sexual selection. Sexual selection is a special case or adjunct to natural selection. This type of selection acts on an organism's ability to successfully attract a mate. One of the key words being "successfully". After all, you can't pass on a trait if you don't produce offspring. Sexual selection acts on the "attractiveness" of an individual to the opposite sex. I put that word in quotes because attractiveness is different in each species. In many species this type of selection leads to sexual dimorphism, where one sex looks different from the other, often as a result of ornamentation or primary sexual characteristics. In some cases a trait will go so extreme that natural selection acts upon it -- if your trait decreases your survival ability to the point where you do not live long enough to reproduce then that extreme trait gets removed from the population. The attractive trait doesn't necessarily have to be some type of bodily ornamentation. It can be courtship dances, nuptial gifts, building elaborate structures/nests, territoriality, combat skills, or any other of a host of things. The overall point is that you have to have or do something that attracts the opposite sex in such a way that it makes you the most attractive of all while still allowing you to survive to reproduce. As with most scientific theories, it gets much more complicated than that, but I think you get the point.

So now let's go back to that picture-this-scenario and add some information based off of what we know about sexual selection and the attractiveness of the human face. We know that facial features that increase a person's attractiveness serve as subconscious cues of biologically important variables such as health. We also know that human faces show marked sexual shape dimorphism, men's faces are different shapes than women's faces. Yeah, I know, a "duh" moment right. Well, just hang with me for this one. It has been found that attractiveness for female faces is related to signs of youth, symmetry, and averageness (an odd term, I know, but basically meaning 'not weird looking'), and that these features signal health, femininity, and fertility. Male faces are considered to be more attractive with increased symmetry and averageness. But as many women will tell you, greater masculinity does not always go hand-in-hand with greater attractiveness. In this instance, I'm using the word "attractive" to relate to facial features rather than an overall impression - thing pretty boy vs. tough guy. However, many women will also tell you that both the pretty boy and the tough guy can be attractive, just not necessarily in the same way.

The shapes of the human faces themselves are also important. Highly feminine faces tend to have relatively large eyes, smaller brow ridges, smaller jaws, and fuller lips. Attractive male faces tend to have longer and wider jaws, relatively smaller top halves and eyes, and more prominent brow ridges. Those descriptions I'm taking right from the article even though they tend to conjure up a rather funny looking person in my mind's eye. Anyway, its all related to genes and hormone levels during puberty. A topic better left for another post. For this particular study it is also important to note that humans show marked height dimorphism as well. Men, in general, are taller than women.

So far I've been relaying information (mostly) from a study I came across recently, published in the journal Evolutionary Psychology, about the evolutionary origin of the shape dimorphism in human faces and how that is related to height dimorphism. In layman's terms, does the angle or tilt at which you see someone's face make them more or less attractive?

Now, picture your perfect mate not just as a set of handsome/pretty characteristics but those characteristics on a person standing right in front of you. What do you see now?

This study had participants complete two tasks designed to measure the masculinity/femininity of a face as well as rate their attractiveness. They used a 3D face modeling program that manipulated the portrayed pitch of a model - untilted (straight), tilted slightly upwards, further upwards, slightly downwards, and further downwards - while using "examples of unattractive, real, attractive, and average" faces of the sexes.

They found that the pitch of the face directly influences its perceived masculinity/femininity and affects its perceived attractiveness. They found that an upward tilted face is judged to be more masculine (or less feminine in female faces) and downward faces judged to be more feminine (or less masculine in male faces). Sure, that makes sense, especially when you factor in the height dimorphism. Think about it: A male is taller than a female, the male viewing the female from above perceives her face as tilting down, the female viewing the male from below perceives his face as tilting up. Remember those funny sounding descriptions of the attractive faces (jaws, brow ridges, etc.)? Why those shaped features? Perhaps they are due to divergent sexual selection pressures that resulted in the selection for male and female faces that had these pitch perspective differences as part of their typical proportions. Or maybe they are more related to behavior. The authors draw a parallel between the dominance/appeasement displays of other species - stretching/rearing vs. crouching/bowing. Upward tilting faces are more dominant than downward tilting faces. I gotta say, the little feminist voice in my head cringes at that one.

So, was your picture-this perfect mate tilting their head upward or downward?

Wednesday, December 8, 2010

I just saw the new Harry Potter movie and so decided to type the general search term "Harry Potter" into a few science literature search engines just to see what got conjured up. One of the first topics was all about the heritability of magic!

A correspondence in Nature suggests that magical ability is inherited in a Mendelian fashion, with the wizard allele (W) being recessive to the muggle allele (M). The recessive part makes since considering there are so many more muggles, those without magical abilities, than there are witches/wizards. That means that those with magical ability must have two copies of the wizard allele (W W). Take this up the family tree and it means that purebloods will have both parents that are W W while half-bloods and mudbloods will have one or both parents with W M. Although, Harry does have a W W genotype he is not considered pureblood since his mother was muggle-born. Later published comments point out some interesting flaws in this particular hypothesis.

Another paper, published in BMJ, discusses in more detail the evidence for a genetic basis to magic. As we discussed above the books, and the movies, to some degree, class people as either muggles, squibs, mudbloods, or purebloods. Most of the world is made up of muggles, a minority of people are witches/wizards, those with magical abilities, and a very small fraction of the magic community are squibs (non-magical people from an otherwise magical family). This suggests that there is some heritability to the trait that is magical ability. Additionally, the environment Harry was raised in, a very non-magical muggle home, further supports that this is a genetic trait, one leaning more towards the nature rather than the nurture.

This particular paper prefers the idea of magical ability not as a dichotomous trait but rather a quantitative attribute that ranges in its ability with some individuals having an exceptional proficiency and others a relative ineptitude. Individual magical skills such as parseltongue (ability to talk to snakes), clairvoyance, metamorphmagus (ability to change physical appearance) are all likely skills that seem to be conferred by specific genes. The authors argue that the best explanation for the inheritance of magic in the world of Harry Potter is best explained by a multilocus model with a dominant gene for magic, the function of which is controlled epistatically by one or more loci, possibly recessive in nature. The genotypes influence total magical abilities with the allele frequencies differing significantly between populations with magical abilities and those without.

The Celebes Sea is a deep basin (approx. 6200 m) located between the Philippines and Indonesia, at the center of the Coral Triangle. Since its formation in the Eocene (44-42 million years ago) it has been isolated from surrounding deep water by relatively shallow sills. Due to density differences in the water in this basis in relation to the water around it, the water is thought to have long residence times. This area is considered to be a biodiversity hotspot because of the high diversity and endemism of shallow-water corals and fishes as well as being the center of geographical distributions and diversity of lanternfish, hatchetfish, dragonfish, and anglerfish. Considering the high diversity of these shallow water creatures it stands to reason that the deep water fauna may be equivalently diverse even though animal density typically decreases with increasing ocean depth. Finding and studying the creatures found that these depths can be very difficult as they are few and far between and because it is just plain difficult to get down that far.

Meet Teuthidodrilus samae, the squidworm:

This is a new and unusual genus and species of swimming polychaete (marine annelid or segmented worms) recently described in a paper in Biology Letters. T. samae belongs to Acrocirridae as a member of the swimming clade and sister to the "bomb"-bearing clade. As you can see from the picture, it sports a series of 10 large appendages near its head. Hence the likeness to a squid. It is slow moving and found in these very deep waters, and it is likely that similar species can be found in this unique region of the ocean.

Tuesday, December 7, 2010

Its been a little while since I've posted anything. I suppose that's what the "semi-frequent" part of my blog description really means. So for the next couple of posts not only am I going to post them in rapid succession but they will also be slightly older stories. But, I figure, cool science is always cool science and so will allow myself to get away with it.

This story caught my eye because (1) I attended a talk by this researcher when I was in grad school and (2) it is about flying snakes.

You didn't know there were flying snakes? Well, then you are in for a treat, my friend, a real treat. Flying snakes or flying tree snakes belong to the genus Chrysopelea (family Colubridae) which can be found in Southeast Asia, India and southern China. Despite its name the snake doesn't actually fly. When they launch themselves off a tree they flatten their bodies and undulate to glide to their destination. Basically its body becomes like a big wing ideal for gliding.

The Paradise Tree Snake (Chrysopelea paradisi) is the most commonly studied of this genus. This snake is brightly colored, with a black body covered from head to tail with a yellow spotting pattern that at times can look stripped and has 5 yellow (sometimes orange) bars that span its width. It is native to the tropical forests of southern Thailand, Peninsular Malaysia, the Philippines, Singapore, and Indonesia. The vegetation in these forests can be quite diverse, including tropical broadleafed species and evergreens with little to no understory. Its diet consists of arboreal reptiles and amphibians (lizards, frogs, etc.) as well as small birds and even bats. Add together habitat and hunting and you can probably start see why this snake needs to fly.

A Virginia Tech researcher, John Socha, studies the kinematics of these snakes. He published a short article in Nature in 2002 (and a similar one in The Journal of Experimental Biology in 2005) where he looked at the full three-dimensional gliding trajectory of these snakes. First, in an open field, he built a 10 meter high tower/platform with a horizontal branch extending from the top. Then he carried his snakes to the top of the platform and videotaped and photographed them jumping off the branch and gliding to the ground. Besides the flying snake (which is obviously so very cool) my favorite part is the undergrad let's-call-them-lackeys running to get the escaping snake once it reaches the ground.

Anyway, he found that the snake prepares for take-off by hanging the front part of its body off the branch looped into a J-shape. When the snake jumps it accelerates up and way from the branch, straightening its body and flattening it by stretching out its ribs. The body width of the snake actually doubles and the stretching of the ribs curves the belly into a concave shape. Because the snake is falling it will gain speed and as it does that it will pitch its body downwards and curve into an S-shape. Then the snake starts undulating from side-to-side, starting at the front and moving down the body. This creates lift and allows it to go a further horizontal distance rather than falling straight down to the ground. C. paradisi is very adept at aerial manoeuvring, being able to turn without banking. It can even out-glide other gliders like flying squirrels (Petaurista petaurista) and flying frogs (Rhacophorus nigropalmatus).

Recently there have been some articles in various major news outlets about Socha's new research presented at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, California and a paper accepted for publication in the journal Bioinspiration & Biomimetics. He explains in further detail the gliding motion of these snakes, having developed a mathematical model that explains how they travel such long distances. Basically it takes the gliding description above and explains it mathematically as well as explaining the gliding techniques of other species (mammals, frogs, lizards, etc.). The U.S. Pentagon and the Defense Advanced Research Projects Agency (DARPA) has had a big interest and funded a lot of this research, although they have yet to explain their big interest in the work.

This is Socha's flying snake page. It includes some great images and videos of his experiments as well as a fantastic links page to find out more about these snakes. I highly recommend checking it out!http://flyingsnake.org/

Welcome to my random, semi-frequent blog which is an interesting mix of serious science, funny stories and videos, and general geekology references. As the title suggests, most will be composed of sciency deliciousness, but expect the unexpected.